Devices comprising nanotubes for use as sensors and/or transducers, and related methods

ABSTRACT

Devices usable as sensors, as transducers, or as both sensors and transducers include one or more nanotubes or nanowires. In some embodiments, the devices may each include a plurality of sensor/transducer devices carried by a common substrate. The sensor/transducer devices may be individually operable, and may exhibit a plurality of resonant frequencies to enhance the operable frequency bandwidth of the devices. Sensor/transducer devices include one or more elements configured to alter a resonant frequency of a nanotube. Such elements may be selectively and individually actuable. Methods for sensing mechanical displacements and vibrations include monitoring an electrical characteristic of a nanotube. Methods for generating mechanical displacements and vibrations include using an electrical signal to induce mechanical displacements or vibrations in one or more nanotubes. Methods for adjusting an electrical signal include passing an electrical signal through a nanotube and changing a resonant frequency of the nanotube.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/767,962, filed Jun. 25, 2007, now U.S. Pat. No. 7,819,005 issued onOct. 26, 2010. The disclosure of which is hereby incorporated herein bythis reference in its entirety.

FIELD OF THE INVENTION

Embodiments of the present invention relate to sensors, transducers, andother devices comprising carbon nanotubes, and to methods of making andusing such devices.

BACKGROUND OF THE INVENTION

Nanotubes are small tubular structures that are conventionally formedprimarily from covalently bonded carbon atoms, although nanotubes formedof other materials (e.g., gallium nitride, boron nitride, carbonnitride, and transition metal sulfides, selenides, halogenides, andoxides) have also been produced. Nanotubes are a relatively recentlydiscovered form of matter. Since their discovery, nanotubes have beenformed having various diameters, lengths, compositions, and structuralforms (i.e., chirality, or twist). The physical, electronic, and thermalproperties that may be exhibited by nanotubes vary broadly and are atleast partially a function of one or more of the size, composition, andstructure of the nanotubes. For example, nanotubes may be electricallyconductive, semiconductive, or nonconductive.

Nanotubes may be formed as so-called single wall nanotubes (SWNTs), orthey may be formed as so-called multiple wall nanotubes (MWNTs). Singlewall nanotubes have a single wall of covalently bonded atoms, whereasmultiple wall nanotubes include two or more generally concentric wallsof covalently bonded atoms. Multiple wall nanotubes may be visualized asone or more nanotubes positioned within another nanotube.

Various techniques may be used to fabricate nanotubes including, forexample, chemical vapor deposition (CVD) methods, arc discharge methods,and laser ablation methods. A background discussion of carbon nanotubes,as well as methods for fabricating nanotubes can be found in, forexample, Dresselhaus et al., Carbon Nanotubes: Synthesis, Structure,Properties, and Applications, Topics Appl. Phys., vol. 80, pp. 1-109(Springer 2001), the disclosure of which is incorporated herein in itsentirety by this reference.

It is known that some physical properties of nanotubes vary withmechanical deformation. For example, it has been shown that theelectrical resistance of a carbon nanotube varies when mechanicaldeformation (i.e., strain) is induced in the carbon nanotube. See, forexample, R. Ciocan et al., Determination of the Bending Modulus of anIndividual Multiwall Carbon Nanotube Using an Electric HarmonicDetection of Resonance Technique, Nano Letters, vol. 5, no. 12,2389-2393 (2005), C. Stampfer et al., Nano-ElectromechanicalDisplacement Sensing Based on Single-Walled Carbon Nanotubes, NanoLetters, vol. 6, no. 7, 1449-1453 (2006), the disclosure of each ofwhich is incorporated herein in its entirety by this reference.Furthermore, it has been proposed in the art to employ nanotubes insensor devices. See, for example, United States Patent ApplicationPublication No. 2004/0004485 A1, published Jan. 8, 2004, United StatesPatent Application Publication No. 2006/0010996 A1, published Jan. 19,2006, and United States Patent Application Publication No. 2006/0283262A1, published Dec. 21, 2006, the disclosure of each of which is alsoincorporated herein in its entirety by this reference.

There remains a need in the art for sensors, transducers, and otherdevices that employ the unique characteristics and properties ofnanotubes in other and further applications, and for methods of makingand using such devices.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a side view of a portion of a first embodiment of asensor/transducer device of the present invention that includes one ormore nanotubes and is suitable for use as a sensor, as a transducer, oras both a sensor and a transducer;

FIG. 2 is a side view of a portion of a second embodiment of asensor/transducer device of the present invention that includes one ormore nanotubes;

FIG. 3 is a side view of a portion of a third embodiment of asensor/transducer device of the present invention that includes one ormore nanotubes;

FIG. 4 is a perspective view of a fourth embodiment of a device of thepresent invention that includes a plurality of individualsensor/transducer devices, each including a nanotube, disposed in anarray across a surface of a substrate;

FIG. 5 is a top plan view of a fifth embodiment of a sensor/transducerdevice of the present invention that includes a plurality of nanotubesensors having varying lengths;

FIGS. 6A and 6B are top plan views of a sixth embodiment of asensor/transducer device of the present invention that includes apiezoelectric device configured to selectively adjust or tune anoperating characteristic of the sensor/transducer device;

FIG. 7 is a top plan view of a seventh embodiment of a sensor/transducerdevice that also includes one or more piezoelectric devices configuredto selectively adjust or tune an operating characteristic of thesensor/transducer device; and

FIG. 8 is a top plan view of an eighth embodiment of a sensor/transducerdevice that includes a plurality of piezoelectric devices configured toselectively adjust the sensitivity, or otherwise tune a nanotube sensor,and that can be used as a sensor or a transducer.

DETAILED DESCRIPTION

As used herein, the term “nanotube” means and includes any elongatedtubular structure having a length and an average diameter, the averagediameter being less than about two hundred nanometers (200 nm).Nanotubes include single walled nanotubes (SWNTs) and multiple wallednanotubes (MWNTs), and may comprise, for example, carbon nanotubes aswell as nanotubes comprising other materials such as, by way ofnon-limiting example, III-V type semiconductor materials, II-VI typesemiconductor materials, boron nitride, carbon nitride, metals, andtransition metal sulfides, selenides, halogenides, and oxides.

As used herein, the term “III-V type semiconductor material” means andincludes any material predominantly comprised of one or more elementsfrom group IIIB of the periodic table (B, Al, Ga, In, and Tl) and one ormore elements from group VB of the periodic table (N, P, As, Sb, andBi).

As used herein, the term “II-VI type semiconductor material” means andincludes any material predominantly comprised of one or more elementsfrom group IIB of the periodic table (Zn, Cd, and Hg) and one or moreelements from group VIB of the periodic table (O, S, Se, Te, and Po).

As used herein, the term “sensor/transducer device” means and includesany device that is suitable for use as a sensor device for sensingmechanical movement, as a transducer device for generating mechanicalmovement from other forms of energy, or as both a sensor device and atransducer device for both sensing mechanical movement and generatingmechanical movement. As used herein, the term “mechanical movement”includes any physical movement of matter in space and includes anyphysical displacement of matter (e.g., strain in a material), as well asvibrations in matter and waves (e.g., acoustical waves, ultrasonicwaves, seismic waves, etc.) initiated in surrounding matter, includingwithout limitation fluid matter.

The illustrations presented herein are not meant to be actual views ofany particular device or system, but are merely idealizedrepresentations that are employed to describe the present invention.Additionally, elements common between figures may retain the samenumerical designation.

A first embodiment of a sensor/transducer device 10 of the presentinvention is shown in FIG. 1. As will be discussed in further detailbelow, the sensor/transducer device 10 may be used as a sensor device,as a transducer device, or as both a sensor device and a transducerdevice.

The sensor/transducer device 10 includes at least one conductive orsemiconductive nanotube 12 having a first end 13A structurally andelectrically coupled to a first electrode 14 and a second, free end 13Bpositioned proximate, but separated from, a second electrode 16. Thefirst electrode 14 may be used to structurally secure (i.e., anchor) thefirst end 13A of the nanotube 12 to a surface 19 of a substrate 18. Asshown in FIG. 1, in some embodiments, the second end 13B of the nanotube12 may be positioned vertically over the second electrode 16. Inadditional embodiments, however, the second end 13B of the nanotube 12may be positioned vertically under a second electrode, laterally besidea second electrode, or in any other position relative to the secondelectrode 16 such as, without limitation, within an end of a tubular orotherwise hollow second electrode.

The substrate 18 may comprise any of a number of materials includingpolymers, ceramics, metals, and semiconductor type materials. By way ofexample and not limitation, the substrate may comprise a silica orsapphire type substrate. In additional embodiments, the substrate 18 maycomprise a wafer. As used herein, the term “wafer” means any structurethat includes a layer of semiconductor type material including, forexample, silicon, germanium, gallium arsenide, indium phosphide, andother III-V or II-VI type semiconductor materials. Wafers include, forexample, not only conventional wafers but also other bulk semiconductorsubstrates such as, by way of non-limiting example, silicon-on-insulator(SOI) type substrates, silicon-on-sapphire (SOS) type substrates, andepitaxial layers of silicon supported by a base material. Semiconductortype materials may be doped or undoped. If the bulk material of thesubstrate 18 is not electrically insulative, a dielectric material (notshown) may be used to electrically isolate the first electrode 14 andthe second electrode 16 from the bulk material of the substrate 18.

Although not shown in FIG. 1, additional conductive structuresincluding, for example, conductive traces, conductive vias, andconductive pads may be formed on the substrate 18, in the substrate 18,or both on and in the substrate 18 for communicating electrically withthe first electrode 14 and the second electrode 16 of thesensor/transducer device 10.

In this configuration, a voltage may be applied to the first electrode14 (and, hence, the nanotube 12, which is in electrical contact with thefirst electrode 14) to generate or affect a capacitance between thenanotube 12 and the second electrode 16. The capacitance between thefirst electrode 14 and the second electrode 16 may at least partiallydepend on the distance between the second end 13B of the nanotube 12 andthe second electrode 16. The sensor/transducer device 10 then may beused to detect any change in the capacitance between the first electrode14 and the nanotube 12, which would indicate a change in the distancebetween the second end 13B of the nanotube 12 and the second electrode16. Such changes might be induced by, for example, mechanical movementof or in the substrate 18, or mechanical movement in a mediumsurrounding the nanotube 12.

In one particular non-limiting embodiment, the sensor/transducer device10 may be used as an acoustical sensor device for detecting andcharacterizing sound waves (i.e., an audible signal). The electricalsignal (i.e., waveform) of the capacitance between the first electrode14 and the nanotube 12 may be a function of one or more characteristicsof the sound waves (e.g., the frequency of the sound and the soundpressure). This electrical signal generated by the sensor/transducerdevice 10 may optionally be reproduced and amplified, either as agraphic waveform, or as physical sound (i.e., an audible signal) usingconventional audio reproduction methods.

In an additional non-limiting embodiment, the sensor/transducer device10 may be used as a sensor for detecting and characterizing mechanicalmovements other than sound waves. Any movement of or in, the substrate18 (e.g., mechanical strain in the substrate 18 or in a mediumsurrounding the nanotube 12) may cause a change in the distance betweenthe second end 13B of the nanotube 12 and the second electrode 16. Sucha change may be detected as a change in the capacitance between thefirst electrode 14 and the nanotube 12 in the same manner as thatpreviously discussed. The electrical signal generated by thesensor/transducer device 10 may optionally be reproduced and amplified,and used to characterize the movement that has been detected using thesensor/transducer device 10.

In yet additional embodiments, the sensor/transducer device 10 also maybe used as a transducer for generating mechanical movement from otherforms of energy, such as, for example, electrical energy. By way ofexample and not limitation, a voltage may be provided between the firstelectrode 14 and the second electrode 16, and the magnitude and/orpolarity of the voltage may be selectively varied. As the magnitudeand/or polarity of the voltage is selectively varied, electrostaticforces may be selectively applied between the nanotube 12 and the secondelectrode 16, and these electrostatic forces may induce movement orvibrations of the free second end 13B of the nanotube 12. In otherwords, the electrostatic forces may be used to selectively inducemovement or vibrations in the nanotube 12. The movement or vibrationsmay be transmitted through the substrate 18, or through a mediumsurrounding the nanotube 12.

In FIG. 1, the nanotube 12 is illustrated as being suspended in air. Inadditional embodiments, however, the nanotube 12 may be suspended in,and surrounded by, a gas, a liquid, a solid material, or any othermedium, or the nanotube 12 may be disposed in a vacuum. In all but thelatter case, the mechanical movement (e.g., vibrations) of the nanotube12 may be transmitted through the surrounding medium (i.e., matter),through the substrate 18, or through both the surrounding medium and thesubstrate 18. If the nanotube 12 is disposed in a vacuum, the mechanicalmovement (e.g., vibrations) of the nanotube 12 may be transmittedthrough the substrate 18.

In view of the above, the sensor/transducer device 10 may be used asboth an emitter of mechanical or acoustical waves or vibrations, and asa receiver (i.e., a detector or sensor) of mechanical or acousticalwaves or vibrations.

As one particular non-limiting example of a manner in which thesensor/transducer device 10 may be used, the sensor/transducer device 10may be embedded in a material or materials (e.g., a laminate) of anyother product or device and used to detect formation of cracks ordefects therein. For example, a sensor/transducer device 10 may beembedded in a microelectronic device (e.g., an electronic signalprocessor device or an electronic memory device). An electrical pulse orsignal may be used to generate and emit a mechanical wave in thesurrounding medium or media of the microelectronic device. Any defectsor cracks in the surrounding medium or media of the microelectronicdevice may reflect one or more waves emitted from the sensor/transducerdevice. Therefore, after emission of the wave, the capacitance betweenthe first electrode 14 and the second electrode 16 may be monitored todetect any reflections of the wave. The electrical signal that isgenerated or modulated by the variation in capacitance caused by thereflected waves may be analyzed and used to detect and characterize anydefect or defects within the microelectronic device that caused thereflection of the emitted waves.

As previously described, in the embodiment of the sensor/transducerdevice 10 shown in FIG. 1, the capacitance between the nanotube 12 andthe second electrode 16 may be monitored when using thesensor/transducer device 10 as a sensor to detect mechanical movement ofthe nanotube 12, and the voltage between the nanotube 12 and the secondelectrode 16 may be selectively varied when using the sensor/transducerdevice 10 as a transducer to generate mechanical movement of thenanotube 12. In additional embodiments of the invention, however, acomplete electrical pathway (e.g., circuit) may be provided through ananotube 12, and the current passing through the nanotube 12 may bemonitored when using the device as a sensor.

Such an embodiment of a sensor/transducer device 30 of the presentinvention is shown in FIG. 2, wherein sensor/transducer device 30includes a complete electrical pathway that passes through a nanotube12. The sensor/transducer device 30, like the previously describedsensor/transducer device 10, may be used as a sensor, for detectingmechanical movement, as a transducer for generating mechanical movement,or as both a sensor and a transducer. The sensor/transducer device 30includes at least one nanotube 12 extending between a first electrode 14and a second electrode 16. For example, the first end 13A of thenanotube 12 may be structurally and electrically coupled to the firstelectrode 14, and the second end 13B of the nanotube 12 may bestructurally and electrically coupled to the second electrode 16.

In this configuration, a voltage may be applied across the nanotube 12between the first electrode 14 and the second electrode 16, and themagnitude of the resulting current passing through the nanotube 12 maybe monitored. Deformation of the nanotube 12 may cause the magnitude ofthe current passing through the nanotube 12 to vary responsive todeformation-induced resistance variation exhibited by the nanotube 12.Therefore, any deflection of the nanotube 12 or vibrations of thenanotube 12 may be detected in the electrical signal (e.g., as avariance in the magnitude of the current passing through the nanotube12).

Like the sensor/transducer device 10, the sensor/transducer device 30may be formed on and/or in a substrate 18. Furthermore, the nanotube 12may be suspended in air or any other medium, or the nanotube 12 may besuspended in a vacuum. Furthermore, the sensor/transducer device 30 maybe used in any of the methods and applications previously described inrelation to the sensor/transducer device 10 shown in FIG. 1.

Optionally, an additional conductive electrode 32 may be providedadjacent an intermediate section of the nanotube 12 at a locationbetween the first electrode 14 and the second electrode 16, as shown inFIG. 2. For example, the additional electrode 32 may be formed on asurface 19 of the substrate 18. In this configuration, a capacitance maybe provided between the nanotube 12 and the additional electrode 32using the medium in the gap between the nanotube 12 and the additionalelectrode 32 as a dielectric for the capacitor so formed, and thiscapacitance may vary as the nanotube 12 is displaced or vibrates.Therefore, mechanical movement in the nanotube 12 may be detected bymonitoring the capacitance between the nanotube 12 and the additionalelectrode 32. Additionally, deflections or vibrations in the nanotube 12may be induced by generating a voltage (in the case of vibrations,varying the voltage) between the additional electrode 32 and thenanotube 12 (by way of one or both of the electrodes 14, 16). As aresult, the sensor/transducer device 30 may be used as both a sensor ofmechanical movement and as a transducer for generating mechanicalmovement (e.g., emitting mechanical vibrations or waves). In someembodiments, mechanical movement of the nanotube 12 may be detected andmeasured by measuring variations in the current flowing through thenanotube 12 between the first electrode 14 and the second electrode 16,and mechanical movement of the nanotube 12 may be induced by generatingor varying a voltage, and hence an electrostatic force, between theadditional electrode 32 and the nanotube 12.

As illustrated in the embodiments of the invention shown in FIGS. 1 and2, the nanotubes 12 may be oriented in a generally horizontal directionrelative to a surface 19 of a substrate 18. In additional embodiments ofthe invention, nanotubes 12 may be oriented in a substantially verticaldirection relative to a surface 19 of a substrate 18.

For example, FIG. 3 illustrates another embodiment of asensor/transducer device 40 of the present invention. As shown in FIG.3, the sensor/transducer device 40 includes a nanotube 12 that isoriented substantially vertically relative to a surface 19 of asubstrate 18. The sensor/transducer device 40 extends between, and iselectrically coupled to each of, a first electrode 14 and a secondelectrode 16. As shown in FIG. 3, in some embodiments, a layer ofmaterial 42 may be formed over the surface 19 of the substrate 18, and avia 44 may be formed in the layer of material 42. The nanotube 12 thenmay be formed or positioned within the via 44.

The first electrode 14 may be formed on or in the surface 19 of thesubstrate 18 prior to forming the layer of material 42 over thesubstrate 18, and the second electrode 16 may be formed over the exposedsurface of the layer of material 42 such that the second electrode 16surrounds and electrically contacts an end of the nanotube 12.

Only one sensor/transducer device is shown in each of FIGS. 1-3.Embodiments of the present invention, however, may include a pluralityof such sensor/transducer devices. By way of example and not limitation,FIG. 4 illustrates a portion of a device 50 that includes a plurality ofindividual sensor/transducer devices 30 similar to that previouslydescribed with reference to FIG. 2. As shown in FIG. 4, the device 50includes a plurality of sensor/transducer devices 30 disposed in anarray across a surface 19 of the substrate 18. Each of thesensor/transducer devices 30 includes a nanotube 12 extending between afirst electrode 14 and a second electrode 16, as previously described inrelation to FIG. 2. As shown in FIG. 4, conductive traces 52 thatcommunicate electrically with the first electrodes 14 and conductivetraces 54 that communicate electrically with the second electrodes 16may be formed on or in the surface 19 of the substrate 18. Theseconductive traces 52, 54 may lead to, for example, other integralelectronic devices or systems (not shown) formed on the substrate 18, orthey may lead to contact pads (not shown) or other electrical contactsthat may be used to establish electrical communication with otherelectronic devices or systems not formed on the substrate 18. Suchelectrical devices or systems may be used, for example, to controland/or monitor the individual sensor/transducer devices 30.

With continued reference to FIG. 4, some of the nanotubes 12 of thesensor/transducer devices 30 may be oriented in a first direction, andsome of the nanotubes 12 of the sensor/transducer devices 30 may beoriented in a second direction that is substantially perpendicular tothe first direction. In additional embodiments, the nanotubes 12 of thesensor/transducer devices 30 may be oriented in more than two (anynumber of) differing directions on the surface 19 of the substrate 18.Each sensor/transducer device 30 may be relatively more sensitive towaves impinging thereon in directions that are oriented at anglesgreater than zero (e.g., ninety degrees (90°)) relative to the lengthsof the nanotubes 12. Therefore, mechanical movement in the substrate 18and/or the medium surrounding the nanotubes 12 can be detected orgenerated in any number of directions using the device 50 by orientingthe nanotubes 12 of the sensor/transducer devices 30 in a plurality ofdiffering directions on the substrate 18.

The device 50 may be further configured to enable identification of thedirection and speed of displacements or vibrations propagating throughthe substrate 18 or surrounding medium if the relative locations of thevarious devices 30 and the distances therebetween on the surface 19 ofthe substrate 18 are known. For example, the relative locations of thevarious sensor/transducer devices 30 and the distances therebetween onthe surface 19 of the substrate 18 can be determined after thesensor/transducer devices 30 have been formed on the substrate 18, orthey may be selected prior to forming the sensor/transducer devices 30on the substrate 18.

If the locations and spacings of the sensor/transducer devices 30 areknown, the direction and speed of mechanical movement (e.g., vibrationsor waves) propagating through the substrate 18 or the medium surroundingthe nanotubes 12 may be determined using timing methods. For example, asa wave propagates across the substrate 18 or through the mediumsurrounding the nanotubes 12, an electronic timer (e.g., a computerclock) may be used to measure the time T it takes for the wave to travelfrom a first sensor/transducer device 30 to a second sensor/transducerdevice 30. If the distance D between the first and second devices 30 isknown, the velocity V of the wave may be determined using the equation(V=D/T). Furthermore, by detecting the wave as it impinges on at leastsome of the sensor/transducer devices 30, and the respective relativetimes at which the wave impinges on those sensor/transducer devices 30,the direction in which the wave is traveling also may be determined.

As previously mentioned, each of the sensor/transducer devices of thedevice 50 shown in FIG. 4 may comprise, for example, thesensor/transducer devices 10 previously described with reference to FIG.1 or the sensor/transducer devices 30 previously described withreference to FIG. 2. In additional embodiments, at least some of thesensor/transducer devices of the device 50 shown in FIG. 4 may comprisethe sensor/transducer devices 40 previously described with reference toFIG. 3, or any of the additional sensor/transducer devices describedherein below.

Each nanotube 12 of the sensor/transducer devices described herein mayexhibit one or more (e.g., harmonics) resonant frequencies that are atleast partially a function of the length, diameter, wall thickness andcomposition of the nanotube 12. Furthermore, each nanotube 12 may berelatively more sensitive to frequencies corresponding to the resonantfrequencies thereof. Therefore, in some embodiments, a plurality ofdevices, each having a nanotube 12 exhibiting a different resonantfrequency, may be used to provide a high fidelity sensor and/ortransducer having a sensitivity to a relatively broader range offrequencies.

By way of example and not limitation, the device 50 shown in FIG. 4 maybe modified such that each of the individual sensor/transducer devices30 is replaced with a plurality of individual sensor/transducer devices30A, 30B, . . . 30 n, where n is any integer, each of the individualsensor/transducer devices 30A-30 n having a nanotube 12 that exhibits adifferent resonant frequency or series of frequencies. For example, asshown in FIG. 5, each individual sensor/transducer device 30 of thedevice 50 (FIG. 4) may be replaced with four individualsensor/transducer devices 30A, 30B, 30C, and 30D, each of which has arespective nanotube 12A, 12B, 12C, and 12D. As shown in FIG. 5, each ofthe nanotubes 12A, 12B, 12C, and 12D may be caused to exhibit adifferent base or harmonic resonant frequency by, for example, formingthe nanotubes 12A-12D to have different lengths. For example, the lengthof the nanotube 12B may be greater than the length of the nanotube 12A,the length of the nanotube 12C may be greater than the length of thenanotube 12B, and the length of the nanotube 12D may be greater than thelength of the nanotube 12C. In additional embodiments, the nanotubes maybe provided with any number of lengths. Furthermore, the resonantfrequencies of the nanotubes also may be varied by varying otherfeatures of the nanotubes other than length that affect the resonantfrequency thereof (e.g., the diameter, the wall thickness and thecomposition of the nanotubes 12A-12D).

By using nanotubes 12 having different resonant frequencies as describedabove in relation to FIG. 5, the frequency band sensitivity of thedevice 50 shown in FIG. 4 may be improved. In other words, the number offrequencies of mechanical vibrations or waves that may be sensed orgenerated using the device 50 may be increased.

In additional embodiments of the invention, the frequency bandsensitivity of individual sensor/transducer devices (such as, forexample, the sensor/transducer device 30 shown in FIG. 2) may beselectively variable. For example, another embodiment of asensor/transducer device 60 of the present invention is shown in FIGS.6A and 6B that includes a nanotube 12, the base resonant frequency andharmonics of which can be selectively adjusted.

Referring to FIG. 6A, the sensor/transducer device 60 includes ananotube 12 extending between a first electrode 14 and a secondelectrode 16 in a manner substantially identical to that previouslydescribed in relation to the sensor/transducer device 30 shown in FIG.2. Mechanical waves or vibrations passing through the substrate 18 or amedium surrounding the nanotube 12 may cause movements in the nanotube12, and these movements in the nanotube 12 may be detected by, forexample, applying a voltage V₁ across the nanotube 12 between the firstelectrode 14 and the second electrode 16 and measuring the resultingcurrent passing through the nanotube 12, as previously described herein.

The sensor/transducer device 60 shown in FIG. 6A further includes apiezoelectric element 61 positioned adjacent a section of the nanotube12 at a location intermediate the first electrode 14 and the secondelectrode 16. The piezoelectric element 61 may comprise a piezoelectricmaterial 62 disposed between a first electrode 64 and a second electrode66. As known in the art, piezoelectric materials are materials that willdeform mechanically when an electrical field is applied across thematerial. Piezoelectric materials include, for example, lead zirconatetitanate (PZT), barium titanate, and quartz.

The piezoelectric element 61 may be oriented relative to the nanotube 12such that mechanical deformation of the piezoelectric material 62induced by applying a voltage V₂ between the first electrode 64 and thesecond electrode 66 will cause the piezoelectric element 61 to impingeon, or abut against, the nanotube 12 in such a manner as to alter aresonant frequency of the nanotube 12. In some embodiments, a supportblock 68 may be formed on the substrate 18 on a side of the nanotube 12opposite the piezoelectric element 61, and the piezoelectric element 61may be aligned with the support block 68 and oriented relative to thenanotube 12, such that the nanotube 12 will be pinched between thesupport block 68 and the piezoelectric element 61 when the piezoelectricmaterial 62 is mechanically deformed by applying the voltage V₂ betweenthe first electrode 64 and the second electrode 66, as shown in FIG. 6B.

By causing the piezoelectric element 61 to impinge on the nanotube 12, anode may be effectively formed at the point of contact between thepiezoelectric element 61 and the nanotube 12. Movement of the nanotube12 at this node may be prevented or hindered by the piezoelectricelement 61, and the two resulting sections of the nanotube 12 on eachside of the node may move (e.g., vibrate) independently of the other. Inother words, nanotube 12 of the sensor/transducer device 60 mayeffectively behave as though the nanotube 12 were to comprise twoseparate nanotubes 12, one on each side of the piezoelectric element 61.These two sections of the nanotube 12 may exhibit different resonantfrequencies than those exhibited by the nanotube 12 when thepiezoelectric element 61 is not impinging on the nanotube 12. As aresult, the nanotube 12 may be sensitive to different frequencies whenthe piezoelectric element 61 is impinging on the nanotube 12 than whenthe piezoelectric element 61 is not impinging on the nanotube 12.Therefore, the frequency band sensitivity of the sensor/transducerdevice 60 may be selectively varied by selectively actuating thepiezoelectric element 61.

In some embodiments, the piezoelectric element 61 may be located atapproximately a midpoint along the nanotube 12 between the firstelectrode 14 and the second electrode 16. In additional embodiments, thepiezoelectric element 61 may be located at approximately an integermultiple of any one of ⅓, ¼, ⅕, . . . 1/i of the distance along thenanotube 12 between the first electrode 14 and the second electrode 16,where i is any positive integer. Furthermore, although only onepiezoelectric element 61 is shown in FIGS. 6A and 6B, in additionalembodiments, any number of piezoelectric elements 61 may be locatedalong the length of the nanotube 12, as discussed in further detailbelow.

Optionally, a dielectric material may be provided on one or both of theexterior surface of the nanotube 12 and the exterior surface of thesecond electrode 66 of the piezoelectric element 61 so as to preventcurrent from passing between the first electrode 14 and the secondelectrode 66, or between the second electrode 16 and the secondelectrode 66. In additional embodiments, however, it may be desirable toprovide electrical contact between the second electrode 66 of thepiezoelectric element 61 and the nanotube 12, and to monitor any currentpassing between the first electrode 14 and the second electrode 66,and/or between the second electrode 16 and the second electrode 66.

It is further noted that mechanical strain (e.g., elastic deformation)may be induced in the nanotube 12 of the sensor/transducer device 60, byactuating the piezoelectric element 61 and causing the piezoelectricelement 61 to abut against the nanotube 12. As such, the resistivity(and, hence, the conductivity) of the nanotube 12 may be selectivelyvaried by selectively actuating the piezoelectric element 61 and causingthe piezoelectric element 61 to abut against the nanotube 12. As aresult, the resulting current passing through the nanotube 12 when agiven voltage V₁ is applied between the first electrode 14 and thesecond electrode 16 may vary between two states, one state being that inwhich the piezoelectric element 61 is actuated and impinges on thenanotube 12 and the other being that in which the piezoelectric element61 is not actuated and does not impinge on the nanotube 12. Therefore,the sensor/transducer device 60 shown in FIGS. 6A and 6B also may beused as a modulation element for modulating current flow, as a switchingelement for switching current flow, and arrays of such devices may beused to form memory arrays of electronic memory devices and/or logicarrays of electronic signal processor devices.

Any of the previously described sensor/transducer device 10 (FIG. 1),the sensor/transducer device 30 (FIG. 2), and the sensor/transducerdevice 40 (FIG. 3) also may be provided with one or more piezoelectricelements 61 like that shown in FIGS. 6A and 6B, and may be used asdescribed in relation to the sensor/transducer device 60 with referenceto FIGS. 6A and 6B.

Yet another embodiment of a sensor/transducer device 70 of the presentinvention is shown in FIG. 7. As shown in FIG. 7, the sensor/transducerdevice 70 includes a first piezoelectric element 71 and a secondpiezoelectric element 75. The first piezoelectric element 71 includes apiezoelectric material 72 disposed between a first electrode 73 and asecond electrode 74, and the second piezoelectric element 75 similarlyincludes a piezoelectric material 76 disposed between a first electrode77 and a second electrode 78. As shown in FIG. 7, the firstpiezoelectric element 71 and the second piezoelectric element 75 may beformed on a substrate 18 and aligned with one another along an axis A. Ananotube 12 may be formed or otherwise provided between the secondelectrode 74 of the first piezoelectric element 71 and the secondelectrode 78 of the second piezoelectric element 75 in a substantiallyidentical manner to that previously described in relation to thenanotube 12 and the first and second electrodes 14, 16 shown in FIG. 2.

In this configuration, a first voltage V₁ may be applied between thefirst electrode 73 and the second electrode 74 of the firstpiezoelectric element 71 to generate an electric field across thepiezoelectric material 72. By selectively adjusting the magnitude andthe polarity of the voltage V₁, the first piezoelectric element 71 maybe caused to selectively mechanically deform (e.g., expand and contract)in a direction substantially parallel to the axis A. Similarly, a secondvoltage V₂ may be applied between the first electrode 77 and the secondelectrode 78 of the second piezoelectric element 75 to generate anelectric field across the piezoelectric material 76. By selectivelyadjusting the magnitude and the polarity of the voltage V₂, the secondpiezoelectric element 75 also may be caused to selectively mechanicallydeform (e.g., expand and contract) in a direction substantially parallelto the axis A. By selectively controlling the first voltage V₁ and thesecond voltage V₂, slight variations in compressive and tensile strainmay be induced along the nanotube 12, which may cause slight variationsin the resonant frequencies of the nanotube 12. In other words, theresonant frequencies, as well as the resistivity (and, hence,conductivity), of the nanotube 12 may be selectively adjusted or tunedby selectively varying the first voltage V₁ and the second voltage V₂.

Furthermore, the sensor/transducer device 70 shown in FIG. 7 may be usedas a transducer to generate mechanical movement (e.g., vibrations orwaves) in the substrate 18 and/or a medium surrounding the nanotube 12by selectively controlling a magnitude and polarity of each of the firstvoltage V₁ and the second voltage V₂. The sensor/transducer device 70also may be used as a modulation element or a switching element, aspreviously described in relation to the sensor/transducer device 60shown in FIGS. 6A and 6B.

FIG. 8 is a top plan view of yet another embodiment of asensor/transducer device 80 of the present invention. Thesensor/transducer device 80 includes a plurality of piezoelectricdevices each configured to adjust or tune an operating frequency orfrequencies of a nanotube 12 of the sensor/transducer device 80. Asshown in FIG. 8, the sensor/transducer device 80 may have a first end13A structurally and electrically coupled to a driving elementconfigured to drive oscillations or vibrations in the nanotube 12. Thedriving element may comprise, for example, a piezoelectric element 71that includes a piezoelectric material 72 disposed between a firstelectrode 73 and a second electrode 74, as previously described inrelation to the sensor/transducer device 70 shown in FIG. 7. The firstend 13A of the nanotube 12 may be structurally and electrically coupledto the second electrode 74 of the piezoelectric element 71. A second end13B of the nanotube 12 may be structurally and electrically coupled toanother electrode 16. In this configuration, an oscillating or varyingvoltage V₃may be applied between the first electrode 73 and the secondelectrode 74 to induce mechanical vibrations in the nanotube 12.Concurrently, a voltage V₁ may be applied across the nanotube 12 betweenthe second electrode 74 and the another electrode 16, and the magnitudeof the resulting current passing through the nanotube 12 may bemonitored. As previously described, deformation of the nanotube 12 maycause the magnitude of the current passing through the nanotube 12 tovary. Therefore, any deflection of the nanotube 12 or vibrations of thenanotube 12 may be detected in the electrical signal (e.g., as avariance in the magnitude of the current passing through the nanotube12). The sensor/transducer device 80 may be formed on and/or in asubstrate 18, and the nanotube 12 may be suspended in air, or thenanotube 12 may be suspended in any other medium including a gas, aliquid, or a solid, or the nanotube 12 may be provided in a vacuum.

Although the piezoelectric element 71 is illustrated as being orientedto drive vibrations in a direction generally parallel to the length ofthe nanotube 12, in additional embodiments, the piezoelectric element 71may be oriented to drive vibrations in a direction generallyperpendicular to the length of the nanotube 12, or at any otherdirection relative to the length of the nanotube 12. Furthermore, in yetadditional embodiments, both ends 13A, 13B of the nanotube 12 shown inFIG. 8 may be structurally and electrically coupled to a staticelectrode, or both ends 13A, 13B of the nanotube 12 shown in FIG. 8 maybe structurally and electrically coupled to a driving element, such as apiezoelectric element.

With continued reference to FIG. 8, the sensor/transducer device 80further includes a plurality of piezoelectric elements 61A, 61B, . . .61N (where N is any positive integer), each being positioned at alocation adjacent a section of the nanotube 12 along the length thereof.The piezoelectric elements 61A-61N each may be substantially similar tothe piezoelectric element 61 previously described in relation to FIGS.6A and 6B. Each of the piezoelectric elements 61A-61N may beindividually selectively actuated by applying a respective voltagethereto, as illustrated in FIG. 8. For example, the piezoelectricelement 61A may be selectively actuated by applying a voltage V_(2A),the piezoelectric element 61B may be selectively actuated by applying avoltage V_(2B), and the piezoelectric element 61N may be selectivelyactuated by applying a voltage V_(2N). Each of the piezoelectricelements 61A-61N may be oriented relative to the nanotube 12 such thatmechanical deformation induced by applying the respective voltagesV_(2A)−V_(2N) will cause the respective piezoelectric elements 61A-61Nto impinge on the nanotube 12 in such a manner as to alter a resonantfrequency of the nanotube 12. By way of example and not limitation, aplurality of support blocks 68A-68N may be formed on the substrate 18 ona side of the nanotube 12 opposite the piezoelectric elements 61A-61N,each support block 68A-68N corresponding to and being aligned with oneof the piezoelectric elements 61A-61N. In this configuration, thenanotube 12 may be selectively pinched at any one or more of a pluralityof locations (the locations between the corresponding support blocks68A-68N and piezoelectric elements 61A-61N) along the length of thenanotube 12 by selectively applying the voltages V_(2A)−V_(2N) to therespective piezoelectric elements 61A-61N.

By selectively and individually actuating the piezoelectric elements61A-61N, the resonant frequencies of the nanotube 12 may be tuned oradjusted over a relatively broad band of frequencies.

A sensor/transducer device 80 like that shown in FIG. 8 may be used fora number of different applications, including those previously describedin relation to the sensor/transducer devices described above.Additionally, the sensor/transducer device 80 may be used as anelectronic signal encoder. As previously discussed, a known voltage V₁may be applied between the second electrode 74 and the another electrode16, and the resulting current flowing through the nanotube 12 betweenthe second electrode 74 and the another electrode 16 may be used togenerate an electrical signal. Vibrations then may be induced in thenanotube 12. The characteristics of the electrical signal may varydepending on which, if any, of the piezoelectric elements 61A-61N areactuated so as to impinge on the nanotube 12. Each of the individualpiezoelectric elements 61A-61N may be in either of an actuated state (inwhich the piezoelectric elements 61A-61N impinge on the nanotube 12) ora non-actuated state (in which the piezoelectric elements 61A-61N do notimpinge on the nanotube 12). Therefore, the electrical signal betweenthe second electrode 74 and the another electrode 16 may assume any oneof a number of “states,” depending on which, if any, of the variouspiezoelectric elements 61A-61N are actuated. It is theoreticallypossible for the electrical signal to assume as many as 2 ^(N) differentstates, where N represents the number of piezoelectric elements 61A-61Nin the sensor/transducer device 80. For example, if thesensor/transducer device 80 includes four (4) piezoelectric elements61A-61N, it would theoretically be possible for the electrical signal toassume as many as 2 ⁴ (i.e., sixteen (16)) states, each of which isrepresented in Table 1 below.

TABLE 1 1st 2nd 3rd 4th Piezoelectric Piezoelectric PiezoelectricPiezoelectric STATE Element Element Element Element 1 Not Actuated NotActuated Not Actuated Not Actuated 2 Actuated Actuated Not Actuated NotActuated 3 Actuated Actuated Actuated Not Actuated 4 Actuated ActuatedActuated Actuated 5 Actuated Actuated Not Actuated Actuated 6 ActuatedNot Actuated Not Actuated Not Actuated 7 Actuated Not Actuated ActuatedNot Actuated 8 Actuated Not Actuated Actuated Actuated 9 Actuated NotActuated Not Actuated Actuated 10 Not Actuated Actuated Not Actuated NotActuated 11 Not Actuated Actuated Actuated Not Actuated 12 Not ActuatedActuated Actuated Actuated 13 Not Actuated Actuated Not ActuatedActuated 14 Not Actuated Not Actuated Actuated Not Actuated 15 NotActuated Not Actuated Actuated Actuated 16 Not Actuated Not Actuated NotActuated Actuated

It will be apparent to those of ordinary skill in the art that thesensor/transducer device 80 may be used for base sixteen (16) encodingapplications when the sensor/transducer device 80 includes four (4)piezoelectric elements 61A-61N, and hence is capable of assuming any oneof 16 different states. It will also be apparent to those of ordinaryskill in the art that the sensor/transducer device 80 may be providedwith any other number of piezoelectric elements 61A-61N to enable thesensor/transducer device 80 to be used for other types of encodingapplications (e.g., base ten (10) encoding applications, base thirty-two(32) encoding applications, etc.).

In some embodiments, the piezoelectric elements 61A-61N may bepositioned at locations along the nanotube 12 selected to maximize thetotal number of resonant frequencies or states that may be exhibited bythe nanotube 12. For example, if any of the piezoelectric elements61A-61N are symmetrically situated at equal length on each side of amidpoint along the length of the nanotube 12, at least some of thestates that may be exhibited by the nanotube 12 may be degenerative(i.e., the same or duplicative). Therefore, in some embodiments, thepiezoelectric elements 61A-61N may be located asymmetrically about amidpoint of the nanotube 12, the piezoelectric elements 61A-61N may eachbe situated along only the nanotube 12 on only one side of a midpoint ofthe nanotube 12, or they may be positioned in any other configurationthat reduces or minimizes a number of degenerative states that may beexhibited by the nanotube 12.

The various embodiments of sensor/transducer devices previouslydescribed herein may be fabricated using methods known to those ofordinary skill in the art of microdevice and nanodevice fabrication. Forexample, the sensor/transducer devices may be formed lithographically ina layer-by-layer process. Such processes generally include forming fullor partial layers of material on and/or in a surface of a substrate, andselectively patterning the layers (e.g., removing selective portions ofthe layers) as necessary or desired to form the individual elements andstructures of the sensor/transducer devices being formed. By way ofexample and not limitation, layers of conductive material (e.g., metalsand doped semiconductor materials) may be deposited using, for example,one or more of physical vapor deposition (PVD) techniques, chemicalvapor deposition (CVD) techniques, atomic layer deposition (ALD)techniques, electroplating techniques, and electroless platingtechniques. Layers of dielectric oxide materials (i.e., materials thatare electrically insulative) may be deposited using, for example,physical vapor deposition (PVD) techniques, they may be formed bydepositing a metal layer and subsequently oxidizing the metal layer, orthey may be formed by depositing another oxide precursor material (e.g.,tetraethylorthosilicate (TEOS)) and causing the precursor material toundergo a chemical reaction to form an oxide material (e.g., silica(SiO₂). Etching processes, including wet (e.g., chemical) etchingprocesses and dry (e.g., plasma) etching processes, may be used toremove layers of material or regions of layers of material. Furthermore,such etching processes may be isotropic or anisotropic as necessary ordesired. Patterned mask layers may be used to protect selected portionsof layers of material, while one or more etching processes are used toremove other selected portions of the layers of material layers.Photolithography, imprint lithography (e.g., nanoimprint lithography),electron beam lithography, ion beam lithography, or any other method,including the use of pitch multiplication techniques to achievesub-lithographic feature resolution may be used to selectively patternany layer of material (e.g., layers of conductive material, layers ofsemiconductive material, layers of dielectric material, and mask layers)as necessary or desired. These processes are set forth as non-limitingexamples only and are known to those of ordinary skill in the art. Theparticular methods selected will depend on the materials that aredesired to be used to form the sensor/transducer devices.

Furthermore, in the embodiments of sensor/transducer devices previouslydescribed herein, the nanotubes may be formed in situ during fabricationof the sensor/transducer devices, or they may be formed elsewhere andpositioned on and operably coupled with the sensor/transducer devices.By way of example and not limitation, nanotubes may be formed usingarc-discharge methods, laser ablation methods, or chemical vapordeposition (CVD) methods. For example, in arc-discharge methods, carbonatoms may be evaporated by plasma of helium gas that is ignited by highcurrents passing between a carbon anode and an opposing carbon cathode,and may be used to form both carbon multi-walled nanotubes (MWNTs) andcarbon single wall nanotubes (SWNTs). The anode may be doped with acatalyst material (e.g., cobalt or nickel) to form single wall nanotubes(SWNTs) of carbon using arc-discharge methods. As another non-limitingexample, a carbon target containing a small amount (e.g., about one-halfof one atomic percent (0.5 at %)) of catalyst material (e.g., cobalt ornickel) may be ablated with a laser to form single wall nanotubes(SWNTs) of carbon. As a non-limiting example of a chemical vapordeposition (CVD) method that may be used to form nanotubes, a catalystmaterial (e.g., nanoparticles comprising iron, nickel, cobalt, anothertransition metal, or alloys of such transition metals) may be heated tohigh temperatures (e.g., between about five hundred degrees Celsius(500° C.) and about one thousand degrees Celsius (1,000° C.) in areactor chamber. A hydrocarbon gas (e.g., ethylene or acetylene) may beflowed through the reactor chamber for a period of time.

As will be apparent to those of ordinary skill in the art, a number ofembodiments of devices that employ one or more nanotubes and that may beused as sensors for detecting mechanical displacements or vibrations, astransducers for generating mechanical displacements or vibrations, or asboth sensors and transducers, are encompassed by the present invention.Such embodiments may be used to provide sensor/transducer devices thatmay be relatively more sensitive to a broad range of frequencies, andthat may be tunable to particular resonant frequencies.

Although embodiments of the invention have been described as includingnanotubes, it is also contemplated that nanowires may be used in placeof, or in addition to nanotubes, so long as the electrical and physicalproperties of the nanowires allow the resulting sensor/transducerdevices to function as described herein. As used herein, the term“nanowire” means any substantially solid elongated structure havingtransverse cross-sectional dimensions averaging less than about 50nanometers. For example, it is contemplated that nanowires comprisingzinc oxide (ZnO), another II-VI type semiconductor material, a III-Vtype semiconductor material, or a doped silicon or germanium material,may exhibit electrical and physical properties that would enable asensor/transducer device as described herein, but including such ananowire, to function as described herein.

Embodiments of the invention may be used in a variety of applicationsincluding, for example, sound detection and generation, monitoring ofstructural integrity in buildings, bridges, dams, vehicular componentsand other structures, monitoring of microelectronic devices for defects,monitoring of seismic activity (e.g., earthquake detection andcharacterization), measurement of strain in materials, and many others.Furthermore, embodiments of the invention may be embedded in buildings,bridges, dams, vehicular components, microelectronic devices, or anyother material or structure to facilitate their use in suchapplications. As specific, non-limiting examples, embodiments of devicesof the present invention may be employed, without limitations, inaccelerometers, microphones, speakers, switches, modulators, vibrationsensors, motion sensors, deformation and displacement sensors,vibrators, stability control and motion compensation systems forvehicles, weapons and cameras.

While the present invention has been described in terms of certainillustrated embodiments and variations thereof, it will be understoodand appreciated by those of ordinary skill in the art that the inventionis not so limited. Rather, additions, deletions and modifications to theillustrated embodiments may be effected without departing from thespirit and scope of the invention as defined by the claims that follow.

1. A sensor/transducer device, comprising: at least one nanotube havinga first end structurally and electrically coupled to a first electrodeand a second end structurally and electrically coupled to a secondelectrode; and at least one element located laterally adjacent the atleast one nanotube and configured to adjust a resonant frequency of theat least one nanotube by bearing on a lateral side surface of the atleast one nanotube.
 2. The device of claim 1, wherein the at least onenanotube comprises a plurality of nanotubes, each nanotube of theplurality of nanotubes having a first end structurally and electricallycoupled to a respective first electrode of a plurality of firstelectrodes and a second end structurally and electrically coupled to arespective second electrode of a plurality of second electrodes.
 3. Thedevice of claim 2, wherein the nanotubes of the plurality of nanotubesexhibit a plurality of different resonant frequencies.
 4. The device ofclaim 3, wherein the nanotubes of the plurality of nanotubes havevarying lengths.
 5. The device of claim 1, wherein the at least oneelement comprises at least one piezoelectric element.
 6. The device ofclaim 5, wherein the at least one piezoelectric element comprises aplurality of piezoelectric elements, each piezoelectric element of theplurality of piezoelectric elements configured to impinge on the atleast one nanotube at a different location along a length of the atleast one nanotube.
 7. A sensor/transducer device comprising a pluralityof nanotubes configured to exhibit a plurality of resonant frequencies,each nanotube of the plurality of nanotubes having at least a first endstructurally and electrically coupled to an electrode, wherein at leastone nanotube of the plurality of nanotubes has a first length, at leastone nanotube of the plurality of nanotubes has a second length differingfrom the first length, at least one nanotube of the plurality ofnanotubes being oriented in a first direction, and at least one nanotubeof the plurality of nanotubes being oriented in a second directionoriented at an angle relative to the first direction.
 8. The device ofclaim 7, wherein each nanotube of the plurality of nanotubes has asecond end structurally and electrically coupled to another electrode.9. The device of claim 8, further comprising additional electrodes, eachpositioned proximate an intermediate section of a corresponding nanotubeof the plurality of nanotubes, each of the additional electrodesconfigured to affect or sense a capacitance between each of theadditional electrodes and the corresponding nanotubes.
 10. The device ofclaim 7, further comprising additional electrodes, each positionedproximate a second end of a corresponding nanotube of the plurality ofnanotubes, each of the additional electrodes configured to affect orsense a capacitance between each of the additional electrodes and thecorresponding nanotubes.
 11. The device of claim 7, further comprising aplurality of piezoelectric elements, each configured to adjust aresonant frequency of at least one nanotube of the plurality ofnanotubes.
 12. A method of sensing mechanical movement in a medium, themethod comprising adjusting a resonant frequency of at least onenanotube in the medium while measuring at least one electroniccharacteristic of the at least one nanotube, wherein adjusting aresonant frequency of the at least one nanotube comprises causing atleast one element to impart a force on a lateral side surface of atleast a portion of the at least one nanotube.
 13. The method of claim12, wherein measuring at least one electronic characteristic of the atleast one nanotube comprises measuring a capacitance between the atleast one nanotube and an electrode located proximate the at least onenanotube.
 14. The method of claim 12, wherein adjusting a resonantfrequency of the at least one nanotube comprises generating a tensile orcompressive stress in at least a portion of the at least one nanotube.15. A device, comprising: at least one nanotube carried by a substrate;at least one electrode in electrical contact with the at least onenanotube; and at least one actuable structure carried by the substrateand configured to abut against a lateral side surface of the at leastone nanotube in an actuated position.
 16. The device of claim 15,wherein the at least one actuable structure is configured to impart avariable force on the lateral side surface of the at least one nanotube.17. The device of claim 15, wherein the at least one actuable structurecomprises at least one piezoelectric element.
 18. The device of claim17, wherein the at least one piezoelectric element is configured to abutagainst the at least one nanotube at an intermediate location along alength of the at least one nanotube.
 19. The device of claim 18, whereinthe at least one piezoelectric element comprises a plurality ofpiezoelectric elements, each configured to abut against the at least onenanotube at a different location along the length of the at least onenanotube.
 20. A method of encoding, comprising: applying a voltage to ananotube; and encoding an electrical signal by adjusting an electricalcharacteristic of the nanotube using at least one device configured toapply a mechanical force to the nanotube while passing electricalcurrent through the nanotube.
 21. The method of claim 20, furthercomprising selecting the at least one device configured to apply amechanical force to the nanotube to comprise a piezoelectric device. 22.The method of claim 20, further comprising inducing vibrations in thenanotube.
 23. A sensor/transducer device, comprising at least oneelement located laterally adjacent at least one nanotube and configuredto adjust a resonant frequency of the at least one nanotube by bearingon a lateral side surface of the at least one nanotube.
 24. The deviceof claim 23, wherein the at least one element comprises at least onepiezoelectric element.
 25. The device of claim 23, wherein the at leastone element comprises a plurality of elements, each element of theplurality of elements configured to impinge on the at least one nanotubeat a different location along a length of the at least one nanotube.